Astbury, William Thomas

(b. Longton [now part of Stoke-on-Trent], England, 25 February 1898; d. Leeds, England, 4 June 1961)

X-ray crystallography, molecular biology.

Astbury was brought up in the pottery town of Longton. He read chemistry at Cambridge and began research under Sir William Bragg at University College, London, in 1921, moving with him to the Royal Institution in 1923. In 1928 Astbury was appointed lecturer in textile physics at the University of Leeds, then reader, and finally professor of biomolecular structure.

In London, Astbury worked on the structure of tartaric acids, measured diffraction intensities photometrically, and, with Kathleen Lonsdale, produced the first tables of space groups. His assignment at Leeds was the structure of natural and synthetic fibers, especially wool. In 1930 he discovered that two diffraction patterns can be produced from the same wool fiber by exposing it to the X-ray beam when relaxed and when under tension. On the meridian the relaxed fiber showed a prominent spot at 5.1 A., and the stretched fiber a spot at 3.4 A. Astbury concluded that the long polypeptide chains which make up the keratin fiber are folded into a series of hexagons resembling diketopiperazines in structure, and are spaced 5.1 A. apart. When the wool fiber is stretched, these hexagon folds are pulled out into long chains in which the residue repeat is at 3.4 A. He noted the similarity of this stretched, or beta, form of keratin to silk, and proposed for both a twodimensional grid structure, the cross-links between the polypeptide chains being through salt linkages and sulfur bridges.

Henceforth, Astbury’s work was dominated by this theory of the reversible transformation of keratin. In 1940 Hans Neurath showed that the amino acid side chains could not be accommodated in his structures, so in 1941 Astbury, with Florence Bell, modified them; but when the alpha helix and pleated sheets were proposed by Linus Pauling in 1951, Astbury’s models were discarded.

In 1937 Astbury and Florence Bell took the first good X-ray pictures of sodium thymonucleate and discovered the strong meridional spot at 3.4 A. In 1946 Astbury assigned this spot to the eighth layer line, and Mansel M. Davies built a single-chain “pile of plates” model with a chemical repeat at 27 A. From model-building, Davies recognized that the planes of sugar and purine or pyrimidine must be at right angles and that the most likely phosphate ester linkages are between C3 and C5.

Although Astbury’s structures for proteins were all wrong in detail, they represent the first attempt at molecular models in which specific cross-linkages hold the polypeptide chains in a characteristic conformation. His suggestion of the folding and unfolding of these chains as the basis of extensibility of fibrous proteins and of the denaturation process of globular proteins was correct in essence. Nowhere did he utilize helical models, but his picture of DNA as a dense molecule with the bases stacked one above another 3.4 A. apart was the first step toward the elucidation of its structure.

As a pioneer, Astbury was bound to see his work superseded, but by his enthusiasm and mastery of the art of lecturing he drew others into the then young field of molecular biology. He provided the stimulus to the more detailed and reliable work of his successors.

BIBLIOGRAPHY

I. Original Works. Astbury wrote over 100 papers and two books. J. D. Bernal has published an almost complete bibliography in his Royal Society memoir on Astbury (see below). Astbury’s most important papers are the three he published under the title “The X-ray Studies of the Structure of Hair, Wool, and Related Fibres,” in Philosophical Transactions of the Royal Society, 230A (1931), 75–101; 232A (1933), 333–394; and Proceedings of the Royal Society, 150A (1935), 533–551. His best papers on nucleic acids are “X-ray Studies of Nucleic Acids,” in Symposium of theSociety for Experimental Biology, 1 (1947), 66–76; and “Protein and Virus Studies in Relation to the Problem of the Gene,” in Proceedings of the 7th. International Congress of Genetics [held at Edinburgh in 1939] (Cambridge, 1941), pp. 49–51. Biographical information will be found in “The Fundamentals of Fibre Research: A Physicist’s Story,” in Journal of the Textile Institute, 51 (1960), 515–526. His two books are Fundamentals of Fibre Structure (London, 1933); and Textile Fibres Under the X-Rays (London, 1940).

II. Secondary Literature. The most detailed biography is J. D. Bernal’s, in Biographical Memoirs of Fellows of the Royal Society, 9 (1963), 1–35, with bibliography and portrait. For obituary notices see K. Lonsdale, in Chemistry and Industry (1961), 1174–1175; and I. MacArthur, in Nature, 191 (1961), 331–332.

Robert Olby